1. Field of the Invention
The present invention relates to an insect proof board used as, for example, a building board.
2. Description of the Prior Art
Building boards used for buildings desirably possess insect proof property so as to be not invaded by harmful insects such as termite or the like.
In order to impart insect proof property to boards, there have conventionally been provided a constitution in which a top paint containing an insecticide is lightly applied to the top layer of a colored steel board (for example, JP-A-2003-127272), a constitution in which a coating composition incorporated with colloidal silica, a silane-based water repellent agent, a repellent for ant and the like in an aqueous resin emulsion is applied to a substrate (for example, JP-A-1999-256076), and a constitution in which a liquid insecticide is adsorbed on silica gel particles and is fixed to the surface of a substrate via an adhesive layer (for example, JP-A-2001-158702).
According to the prior art techniques in which an insecticide mixed with a coating composition is applied to a substrate, there has been a problem that the insecticide is diluted with a resin which is a main component of the coating composition, and thus the concentration of the insecticide present on the surface of the coat is low, thereby failing to sufficiently exhibit insecticidal effects of the insecticide.
Furthermore, when an insecticide is mixed with a coating composition, the coating composition after application to the surface of a substrate is usually subjected to heat-drying at a temperature of about 100 to 150° C., whereby the insecticide may be denatured and deteriorated by the heat-drying.
In the constitution in which silica gel particles having a liquid insecticide adsorbed thereon are fixed to the surface of a substrate via an adhesive layer, the silica gel particles are liable to be peeled off from the adhesive layer, and thus it is difficult to provide lasting insecticidal effect.